Development of an experimental BOF rig for lime dissolution investigations in liquid steel making slag

The lime dissolution in the LD converter (Linz-Donawitz) has been a repeatedly in-vestigated process since the 1950s. The purpose of lime and its dissolution are es-sential for an appropriate slag formation with excellent refining effects for an aimed clean steel. Within a cooperation between the IEHK department of RWTH Aachen University and the global playing lime producer Lhoist, the dissolution behavior of different calciferous additives was investigated under BOF-like conditions. For this purpose, a lime dissolution demonstrator was constructed, which simulates the most im-portant lime dissolving conditions in a LD-type BOF, such as in-situ slag formation, temperature course and turbulences. Furthermore, a test procedure was developed, in which an oxygen gas mixture is blown onto an artificial hot metal melt at regular intervals just interrupted for taking slag samples. These samples were analyzed by XRF (X-ray fluorescence) and a slag oxide balance calculation were done. With this procedure, the dissolution behavior of the examined calciferous additives could be investigated and compared with the first 20 % the blowing time of an industrial BOF. The general dissolution mechanisms correspond to the explained ones in scientific literature. Furthermore, a special calciferous product could be investigated concern-ing its dissolution behavior, too. They could further be compared to the behavior of standard steelmaking lime and dolime grades. Besides, the conducted upscaling gives a comparison of the laboratory demonstrator with test course to the BOP. It showed one main difference in the ratio of the laboratory vessel’s height to diameter of factor 36. Concerning the oxygen flow rate, which is one of the main factors in-fluencing the generation of an active slag in the BOF process, the demonstrator is in a good agreement. The conducted measurements of oxygen activity of the slag also showed good compliance with industrial BOF and therefore a comparable good lime respectively dolime dissolution with the aim of satisfying steel refining.